Distributor breaker arm



March 23, 1954 L. VASOLD 2,673,271;

DISTRIBUTOR BREAKER ARM Filed Jan. 26, 1948 INVENTOR. Leo L. l/aso/a/Patented Mar. 23, 1954 DISTRIBUTOR BREAKER ARM Leo L. Vasold, Toledo,Ohio, assignor to The Electric Auto-Lite Company, Toledo, Ohio, acorporation of Ohio Application January 26, 1948, Serial No. 4,391

8 Claims. 1

The present invention relates to electrical circuit interrupters of themake-and-break impact contact type adapted to be used as timers forignition apparatus or breaker arm contact units on ignition systems forengines and relates particularly to the structural formation and methodor process of producing the same.

The invention includes the production of an electrical make-and-breakcontact or breaker arm unit, for a system using a periodic interrupter,made of a very thin ferrous metal, to which is bonded or intimatelyjoined a tungsten or other suitable contact, the unit provided withsufficient ductility and tensile strength to withstand, without.substantial deformation or bending, highly recurrent impacts and whichhas a very high fatigue strength and a long life of efficientfunctioning without material failure in operation.

The invention comprehends the structural formation of a breaker contactlever unit for ignition devices for automotive type engines whichoperates in a very efficient manner at particularly high speeds forconsiderable periods of time and is capable of withstanding, withoutdeformation or rupture failure, the highly recurrent longitudinal andtransverse stresses which occur at high speed, lasting at least fivetimes as long as the conventional breaker contact levers used undersimilar conditions.

The invention comprises an improved means and process or method by whicha lever arm of a ferrous metal andits contact member are veryeffectively bonded or brazed and concurrently heat-treated, to secure apredetermined hardness of the ferrous metal and a very high increase inits fatigue value, increasing thereby its. efficient operating life athigh engine speeds.

The invention embraces a process whereby a predetermined minimum ofhardness is imparted to a high carbon steel member when subjected to abrazing or bonding operation by controlling the cooling rate thereoffrom said brazing or bonding operation.

The invention is inclusive of a process to increase to a predeterminedvalue the hardness of a steel member having a carbon content rangingfrom 0.60% to 0.85% when the member is subjected to a brazing or bondingoperation by controlling the cooling rate and inhibiting thedecarburization thereof.

In the present high speed automotive type of engine it has beennecessary to provide an ignition timer orbreaker'contact lever unit forthe igto high speeds of operation, without failure, such as is demandedin a six-cylinder engine wherein the ignition timer or breaker contactlever has to make and. break the ignition circuit 200 timesa second whenthe engine operates at 4,000 R. P. M. The ignition timer or breakercontact structures which have been previously used, have developedoperative failures after a comparatively short time of operation. Thesefailures have been due to deformations or by the rupture of the leverarm proper.

It is one of the objects of the invention to overcome the performancefailures before enumerated by providing a circuit breaker lever formedfrom a very thin ferrous sheet material and giving to it greatdurability with the proper characteristics to withstand for a very longperiod of time, without deformation or rupture, longitudinal andtransverse stresses and impacts, producing thereby a breaker contactassembly having a very long life of efficient functioning withoutfailure or breakage not only at very high speeds but throughout theoperating range of the engine.

Another object of the invention is the provision of an impact electricalmake and break lever assembly having a very low polar inertia and of ahigher mechanical strength than heretofore available.

Another object of the invention is to provide a breaker arm made of avery thin sheet steel heattreated concurrently with the brazing of acontact point thereto to produce a structure having a very high fatiguestrength and a long life of effi cient operation for use in very rapidperiodic make-and-break electric systems.

Another object of the invention is to improve the structural formationand the physical characteristics of a make-and-break contact lever forengine ignition systems, so that the contact lever operates, withoutdeformation or rupture failure,

artificial atmosphere wherein, the volume ratio of hydrogen and carbonmonoxide is substantially near its equilibrium value for the temperatureof the heat application and carbon content of the steel, by controllingits cooling rate from. the brazing operation and by the. application ofan inhibitor to-the steel member to prevent the.

decarburi zation thereof.

Another object of the invention is to provide an improved method bywhich a lever arm of thin sheet steel and a tunsten contact point arebonded or brazed and concurrently heat-treated, to secure apredetermined hardness and carbon content of the sheet steel to producea very high increase in its fatigue strength, increasing thereby theefficient operating life at high engine speeds of the resulting breakercontact structure.

Another object of the invention is the provision of a method and meansfor producing a lever arm of steel having a carbon content ranging from0.60% to 0.85% including the step of effecting a coating thereon, whichcoating acts in a three-fold manner: (1) as an inhibitor which preventsdecarburization when the lever arm is placed. into a heated zone forbonding its contact member thereto, (2) as means to enhance the bondingof a tungsten contact to the lever arm for producing an effectivecontact breaker arm assembly, and (3) as an inhibitor preventingoxidation not only due to the atmospheric elements but to ozone producedduring its operation as a make-and-break-device in an ignition system.

Among other objects of the invention is the improvement of the breakerarm assembly of the type disclosed in Patent No. 2,054,010 of September8, 1936, to Louis B. Ehrlich.

Other objects and advantages of this invention relating to thearrangement, operation and function of the related elements of thestructure, to various details of construction, to combinations of partsand to economies of manufacture, will be apparent to those skilled inthe art upon consideration of the following description and appendedclaims, reference being had to the accompanying drawings forming a partof this specification wherein like reference characters designatecorresponding parts in the several views. Referring to the drawings:

Fig. I is a View illustrating one step in the process of forming thebreaker arm from a sheet metal blank;

Fig. II is a view i1lustrating another step in the formation of thebreaker arm assembly;

Fig. III illustrates another step in the formation of the breaker armassembly;

Fig. IV is a cross-sectional view taken substantially in line 4-4 ofFig. III;

Fig. V is an elevational view illustrating an embodiment of theapparatus to carry out the method of the invention;

Fig. V1 is an elevational view of the breaker arm assembly;

Fig. VII is a cross-sectional view taken substantia1ly in line l-'| ofFig. VI;

Fig. VIII is a cross-sectional view taken along line 8-8 of Fig. VI; and

Fig. IX is an isometric view of the ignition zimer or breaker contactstructure of the invenion.

The invention has been illustrated as embodied in an ignition timer orbreaker contact assembly adapted to be used for internal combustionenines but it is to be understood that all the features of the inventionare contemplated to be used whenever the same may be found to beapplicable.

Referring to the drawings, in Fig. I is illustrated a blank of asubstantially triangular configuration, from which the lever armembodying the invention may be fabricated. The blank ln'may be punchedor otherwise produced from a sheet of thin ferrous material, preferablysoft, deep-drawing, cold-rolled steel of a. thickness 1 about .013" to.017. I contemplate that the sheet steel should be fully spheroidizedand hav ing a carbon content ranging from 0.60% to 0.85%. To effectivelyproduce a breaker lever assembly embodying the invention, the blank 10is preferably formed by suitabl dies with a longitudinal fold ll alongits medial line, this fold formed into a rib acting as means to increasethe strength and rigidity of the structure and is also bent as at I4 forthe purpose of reinforcing th end portion, upon which is adapted to besecured an interrupter contact.

In making a lever arm embodying the invention, the width of the blank 10is preferably de creased from substantially its central portion to itsend portion providing the reduced section I5 and at each of the cornersthe openings 16 and I8 are provided. In addition, the side portionsextending from the reduced section l5 are bent along the dotted lines ofFig. IIto form substantially parallel spaced walls or flanges l9 and 20.Th bending operation will produce the proper alignment of the openings16 and It to thereby accommodate suitab1e pivotal elements, thus shapingthe blank [0 to form the lever arm 22 shown in Fig. III. The lever arm22 is generally of channel-shaped cross-section having its web or backwall 23 with a central outwardly projecting fold or reinforcing rib I2preferably extending its full length whereby the end portion [5 is of aT-shaped cross section. The end portion l5 of the breaker arm 22 isformed with a projecting planar end surface or plateau 25,

preferably of circular contour and somewhat above the level of thesurface of the back wall 23. The plateau 25 is formed to carry inintimate or bonded relation the interrupter contact.

A feature of the invention is the provision of an inhibiting agent tothe ferrous material from which the lever arm is fabricated. Theinhibiting agent may be applied to the sheet steel by suitable means,preferably by covering the same after a suitable configuration has beengiven thereto and in carrying out the invention it is contemplated thatthe inhibiting agent of the invention should be applied as an enclosuresuch as a coating to the lever arm prior to the bonding thereto of theinterrupter contact. The inhibiting agent of the invention preferablytakes the form of a coating 26, particularly shown in the cross-sectionof Fig. IV. The inhibiting enclosure or coating of the invention acts ina three-fold manner: (1) as an inhibitor which prevents decarburizationwhen the lever arm is placed into a heating zone for bonding or brazingthe interrupter contact thereto, (2) as means to enhance the bonding orbrazing of a tungsten contact to the lever arm for producing aneffective contact breaker arm assembly. and (3) as an inhibitorpreventing oxidation not only due to the atmospheric elements but toozone caused by the interrupting of an electric circuit during thenormal operation of the arm as a make-andbreak device in an ignitionsystem.

I have found that the invention can be best fulfilled when theinhibiting agent takes the form of a very thin nickel coating which, forsake of economical manufacture, can be .0001" or .0002. However, thethickness of this coating may be of a greater dimension, and theapplication of the inhibiting agent of the invention asa thin coatingcan be economically carried out by electroplating the arms to: give thenickel covering, as is well known the art.

After the application. of. the inhibitor or. nickel coating 2.6; thesurface of. the breaker arm 22 is. adapted to have bonded. thereto aninterrupter contact This contact may take the form of a disc of.tungsten or other suitable material capable of withstanding themechanical stresses and the deleterious effects caused by its use as animpact current interrupter in an ignition system.

In the manufacture of the breaker arm assembly, the contact 30 isadapted to be placed with a linking wafer 32 of the bonding or unitingmember on the end portion 25 of the breaker armas shown in Fig. 11-1.The uniting mem ber contemplated may take the form of a brazing agenthaving a flow point between 1600 F. and 21-00 E. and preferably formedof electrolytic copper or of a cuprous alloy. However, the linking wafer32 may be formed of other metals or a combination of metals whicheffectively wets and bonds the contact 39- to the nickel-plated surface25' of arm lever 22, provided their flow point is lower than the meltingpoint of the metal of the arm or contact member. As a specific example,it has been found that a disc of .138" to .152" diameter and of athickness of .006 to .010" of the electrolytic copper or of anapproximate 8'%- nickel copper alloy produces a very effective bondingbetween the contact element 30 and. the breaker arm surface 25.

In the practice of the invention, the interrupter contact 30 and linkingwafer 32 are placed and retained in position on the end surface 25 ofbreaker arm 22 by a suitable supporting standard or block 35. Thesupporting standard 35 is usually made of carbon or other heat-resistingmaterial not likely to be burned or consumed when placed in the heatingzone of a bonding or brazing furnace. In Fig. V the block 35 is shown asholding one breaker arm and contact assembly, but in practice, aplurality are supported by said standard.

In carrying. out the invention, the block 35 supporting the breaker armand contact assembly is preferably inserted into a suitable electricbrazing furnace such as the conveyor, pusher or manually operable typesadapted to receive an artificial atmosphere. The furnace illustrated. inFig. V is of the pusher type and comprises a receiving table 37, aheating zone. 38 with a manually operable or controlled sliding closure39 and provided with electrical heating units controlled by suitablemeans 40 toregulate the furnace temperature and adapted to be energizedfrom a source of current by means of switching means M. The furnace isprovided with com cluits 43 and 44 for introducing under pressure theartificial atmosphere to realize the invention. After the heating zone38,. the furnace is provided with a cooling zone or heat-treatingsection 45 which is surrounded by cooling jacket 46 serviced by inletand outlet pipes 43 and 45 connected to a source of cooling fluid suchas cooling water through valves 50 and. to regulate the flow and therebythe temperature. The end of the heat-treating section or cooling zone 45has a discharge table 5] and is provided with a sliding closure 52manually operated or controlled.

The manual control for the closures 39 and 52 may be interconnected ormay take the form of pull handles 53, 53 connected respectively tolevers 54, 54' and chain 55, 55' in turn connected to the respectiveclosure 39 or 5.7., so that, as

desired by the operator, manipulationof' the. pull handle: 53101: 53:raises or: lowers the closures 39 and 5-2.. Adjacent to: the closures39': and 52, which block the inlet: and outlet of the brazing electricfurnace, are gas jets 56- and 51 adapted to. insure the efiectivecontrol of the artificial atmosphere as gas will be ignited whenever theclosures are open or: as it escapes from the closures, forming thereby acurtain blocking the ingress of air into the furnace. However, othersuitable means to prevent the ingress of air into the furnace iscontemplated.

The brazing furnace to carry out the invention is' illustrated as of thepusher type and by placing on thereceiving table 37. the blocks 35 andbreaker arm contact assembly contained therein one after the other, thesame may be pushed into the furnace heating. zone 38' where the breakerarm 22 and interrupter contact 30 are bonded together. The temperatureof the heating zone of the furnace 38. is preferably kept at a valuesufficient to cause the brazing agent 32 to flow or fuse, wetting thelever surface 25, bonding thereto the interrupter contact 30, insuringthereby the proper position and intimate connection of the contact onthe breaker arm when the linking metal or brazing alloy solidifies. Inpractice. the temperature of the furnace may be held at approximately2050 Fa However, this tempera-- ture should be correlated with the flowpoint of the brazing agent or linking alloy used and may range from1600" F. to 21-00 F. The time of heat application contemplated for thebonding and heat-treating operation or the period of time during whichthe lever arm 22 and its con tact assembly is retained in the heatingzone under an artificial atmosphere may be corre lated and governed bythe temperature of the furnace and the carbon content of the materialfrom which the lever arm 22 is formed, as well as by the flow point ofthe brazing or the linking alloy 32 used and should be of sufiicientduration to soak or permeate the arm to impart a uniform temperaturethereto.

The artificial atmosphere having av low dewpoint contemplated to beintroduced above atmospheric pressure into the heating zone and coolingvchamber of the brazing furnace, while the arm 22 and contact assembly 30are being bonded or during the brazing operation, is one wherein thevolume ratio of hydrogen and carbon monoxide is substantially near itsequilibrium value for the temperature of the heat application and carboncontent of the steel from which the lever arm 22 is formed.

As a specific example of the type of artificial atmosphere contemplated,it has been found that the same can be attained by cracking producer gashaving an average B. tu. content of 550.

The cracked gas then has-the following nominal composition:

Oxygen None.

Carbon dioxide None to trace. Carbon monoxide 20% to 21%. Hydrogen 39%to 40%. Methane 1% to 3%. Nitrogen--. 38% to 39%.

The above analyses are those produced by the gas cracker when thedew-point ranges between 15 F. and 30 F. This atmosphere is inapproximate equilibrium with an approximate .75% carbon steel atapproximately 2015 F. This atmosphere may be considered. chemicallyinacti-veat thetemperature.specified or one wherein the potentialitiesof the nickel inhibitor to prevent decarburization of the steel memberare fully realized. Satisfactory results have also been secured when theartificial atmosphere introduced under pressure into the brazing furnaceis produced as the result of cracked ammonia gas which, on volume basis,may consist of three volumes of hydrogen and one volume of nitrogen ofvery low dew-points.

As a specific example of the brazing and heat application of theinvention, the same can be fulfilled when the lever arm is fabricated ofa fully spheroidized sheet steel having as its main constituents: carbon.70 to 80, manganese .50 to .80, phosphorus, .03 max, sulphur .03 max,silicon .15 to .30 and having a hardness of Rockwell T 84 to 86. The armnickel-plated with a coating ranging from .0001" to .0002, the brazingoperation occurring at a furnace temperature ranging from 2000 F. to2100 F. in an artificial atmosphere of the types before specified andperformed by using as bonding agent a copper wafer or a copper nickelbrazing alloy, the time of retaining the breaker arm and contactassembly in the heating zone of the furnace being approximately six toeight minutes.

An important feature of the invention is the control of the rate ofcooling of the arm from the brazing operation, which control is suchthat a predetermined hardness is imparted thereto. In this form of theinvention, the control of the cooling rate from the brazing operation isaccomplished by moving rapidly the block holding the arm and contactassembly from the heating zone into the cooling zone to secure, ineffect, a heat-treating operation of the steel from which the arm ismade.

The temperature of the cooling zone and the rapidity by means of whichthe arm with its bonded contact is moved thereinto to secure the rate ofcooling to fulfill the invention is subject to many variables and can bebest established through the end result as manifested by the hardness ofthe lever arm after the same is withdrawn from the cooling zone into thedischarging table. It is contemplated that the temperature and thecontrol of the rate of cooling of the arm be such that an arm made ofsteel having a carbon content ranging from 0.60 to 0.85% will test to aminimum hardness of Rockwell B 85 corresponding to Rockwell -T 58.

In practice, it has been found that a breaker arm assembly including anarm of a carbon content ranging from 0.60% to 0.85% and having ahardness ranging from Rockwell 45-1 58 to 74 or one possessing ahardness which ranges from 20 to 45 Rockwell C fulfills the mainobjectives of the invention with respect to the proper characteristicsof fatigue strength, durability, and efficient operating life withoutfailure at very high speeds. Therefore, the temperature of the coolingzone and the rapidity of moving the bonded arm thereinto should be socontrolled to secure the hardness hereinbefore specified, andparticularly with the Rockwell hardness ranging from 20 to 45 C, thesame canbe secured through a proper control by using a very lowtemperature coolant and imparting to the cooling chamber a lowtemperature.

In determining the rate of cooling required, it has been found advisableto establish the same by trial runs, testing the hardness of the endproduct such as a brazed breaker arm assembly and noting the temperatureof-the incoming coolant, position of valves 50 and 50 and thetemperature of the jacket 46. As a specific example, satisfactoryresults have been secured when the temperature of the jacket is retainedat approximately 75 to for a comparatively short cooling zone furnace.However, the desired hardness has been secured when the temperature ofthe jacket is kept at approximately 70 F. using cooling water having atemperature not above 60 F. for a relatively long cooling zone furnace.

It is contemplated that the amount of the bonding agent 32 should notonly produce an intimate bond between the breaker arm surface 25 and thecontact 30, but will flow bonding the contiguous walls of thereinforcing rim I2, as is particularly shown in Figs. VII and VIII,thereby serving a dual purpose.

A breaker arm assembly produced from steel with the carbon contentspecified covered with the inhibiting agent of the invention with acontact bonded by brazing the same under the conditions hereinbeforeoutlined and wherein the rate of cooling has been controlled, ashereinbefore specified, provides a resulting structure which has thedesired hardness and a very high fatigue strength. The breaker contactlever, produced in accordance with the invention, is characterized asbeing rust-proof, non-oxidizable by ozone, having partial lamellarpearlitic structure with no decarburized areas such as manifested byfree ferrite, and of sufiicient ductility so that the surface at thepivotal end of the arm adja- 7 cent to the openings I6 and I8 may bendto a wide angle such as 90 without fracture.

The means contemplated for the breaker arm to form the same as an impactcontact for an electrical make-and-break device of an ignition systemare illustrated in Fig. IX and comprises a spacing and reinforcingmetallic bushing 60 located in the aligned openings l6 and ill of thebreaker arm lever 22. The bushing 60 has reduced ends forming shouldersadapted to be engaged by the inner surface of the side walls l9 and 20and the end portions projecting through the aligned openings are swedgedover the side walls, as at 6|, in order to retain them in proper spacedposition. The bushing 60 snugly retains an insulating bushing 62 whichserves as a pivotal insulating bearing for the arm assembly about apivotal post, not shown.

Between the parallel walls l9 and 20 of the breaker arm lever 22 isfixedly secured to the web section 23 an L-shaped rubbing block 65 bymeans of suitable rivets 61 and 68 which also serve to secure anelectric current conducting strip 10. The conducting strip l0 forms anefficient connection-for reducing the electrical resistance for the flowof current to the contact 30 through the breaker arm structure. Therubbing block is preferably of an L-shaped formation made of anonconducting material, preferably a fabric permeated or stiffened witha condensation product. The rivets 61 and 58 are spun against the innerface of the rubbing block as at 12 and urge, by means of the rubbingblock, the conducting strip 20 into very effective contacting engagementwith thenickel-plated surface of the web section 23 of the breaker arm.The rivets 61 and 68 provide very effective means to retain the rubbingblock 35 and strip 10 in proper fixed position and thereby decreases, toa minimum, the number of parts forming the breaker arm assembly of theinvention.

It can be seen-from the foregoing that the invention herein disclosed isa material improvement over the conventional brazing operation and that,by the control of the rate of cooling from said operation to securepredetermined hardness, an effective and very inexpensive method ofheat-treating any steel lmember is provided when the steel member issubjected to a brazing operation. The specific embodiment .of theinvention disclosed produces a breaker arm having physicalcharacteristics and a molecular structurewhich gives a very high fatiguestrength and provides a long life of efficient operation for the breakerarm as an impact contact make-andbreak device for .an electric .circuitsuch as that of an ignition system f orengines. Thecontactarm producedby the invention has a lower polar inertia and a higher mechanicalstrength as well as a higher fatigue strength than heretofore available,so that deformation and rupture are practically avoided under normalconditions of use.

In .describing the invention, in the interest .of clarity, the same hasbeen confined to :brazing of the contact point to a preformed ferrousmember of sheet steel. However, it is .to be understood that theinventionand the procedures disclosed herein are well adapted forbrazing ferrous metals of the carbon content mentioned to secure thephysical and strength characteristics hereinbefore outlined.

It is to be understood that the above detailed description of thepresent invention is intended todisclose an embodiment thereof to thoseskilled in the.art,'but that the invention is not to becon strued aslimited inits application to the details of construction and arrangementof partsillustrated in the accompanying drawings, since the invention iscapable of being practicedand carried out in various ways withoutdeparting from thespirit of the invention. Thelanguage used in thespecification relating to the operation and function of the elements ofthe invention isremployed for purposes of description and not oflimitation, and it is not intended to limit the scope of the followingclaims beyond the requirements of the prior art.

What is claimed:

1. An ignition breaker arm structure comprising a high carbon steel arm,an overall sealing cover solely of nickel directly enclosing said arm, atungsten interrupter contact brazed to said nickel sealing cover, thebrazing of said contact to said nickel sealing cover secured by acuprous brazing alloy having a melting point below that of said nickelcover ranging between 1600 F. to 2100 F. fused therebetween, the saidarm having lamellar pearlite characteristic and a carbon content rangingfrom 0.65% to 0.80% with a hardness ranging from 30 to 45 Rockwell inthe C scale having sufficient ductility to permit bending portions ofthe arm to wide angles without fracture.

2. An ignition breaker arm structure comprising a high carbon steel armplated by an overall sealing covering consisting solely of nickel andwith the interrupter contact brazed to said nickel covering, the brazingof said contact to said nickel sealing covering formed by fusingtherebetween a copper nickel allow having a flow point lower than saidcovering about 2000 F. to 2100 F., said arm formed of fully spheroidizedsheet steel and being characterized after the brazing of the contact byhaving substantially no decarburized areas and a carbon content ofapproximately 0.75% with a Rockwell 45-T hardness ranging from 58 to '74with sufficient ductility to allow bending a 10 nortien .o the m struture t a e a l ove 90 without f a t re 3. In elec tric al periodiccircuit interrupting structures, the mb nat c rising a hi h carbon steelmember, a coating consisting solely of plated nickel sealing completelysaid steel member, a contact member, means uniting said contact member.to the nickel coating including a copper nickel brazing alloy of alower melting point than said nickel coating fused between contactmember and coating, said brazing alloy having a, flow pointbetween 2000F. and 2100 F; the said steel member having a carbon cantent rangingfrom 0.70% to 0.80% with a Rockwell hardness ,of at least in the B scalehaving suflicient ductility to allow bending portions of the structureto substantially right angles without fracture and the nickel coating onsaid steel member inhibiting .decarburization during the brazingoperation while increasing the strength of the bond between the contactand member and preventing oxidation during its normal operation as aperiodic circuit interrupter.

4. An electric impact current conducting structure, comprising a highcarbon steel member having a contact. supporting surface, a thin platedcoating consisting solely of nickel forming an in-- hibiting sealingenclosure for said steel member and its contact supporting surface, atungsten contact member brazed to said contact supporting surface by acopperbrazing alloy having a how point below the melting point of saidnickel enclosure, vthe brazing alloy having a fiow point ranging from2000 Rte 2100 F. interposed and fused uniting said contact to the nickelcoating onsaid contact supporting surface, and said steel membercharacterized after the contact has been brazedto the nickel coating onsaid contact supporting surface by having lamellar pearlitecharacteristics with substantially no decarburized areas and with acarbon content ranging from 0.60% to 0.80% with a Rockwell hardnessranging from 58 1707.4 Rockwell 45-T in which sufficient ductility isretained for bending parts thereof at a wide angles without fracture.

5. The method of producing a make and break contact arm assembly whichcomprises forming the arm from sheet steel fully spheroidized having acarbon content ranging from 0.60% to 0.80%, plating directly on said armby electrodeposition a sealing cover consisting solely of nickel,bonding a make and break contact to said plated arm by brazing in anartificial atmosphere which prevents decarburization a tungsten point tothe nickel sealing cover by fusing therebetween a brazing alloyconsisting of copper and 8% of nickel in a heating zone at a temperaturebelow the melting point of said nickel cover ranging from 2000" F. to2100 F., and controlling the cooling rate of the plated arm with itbrazed contact while being subjected to said artificial atmosphere afterthe brazing operation in the heating zone to impart to the arm ahardness ranging from 30 to 45 Rockwell C scale and sufiicient ductilityso that portions of the arm will bend to at least a angle withoutfracture and producing a very strong bond between the tungsten point andthe steel arm with a material increase in th fatigue strength of theassembly.

6. The method of increasing the fatigue strength of a high carbon steelmember for a make and break contact assembly having a carbon content of0.60% to 0.80% when the member is subjected to a brazing operation forbond- 11 ing a contact to the member which comprises completely coveringsaid steel member by electro-depositing thereon as an inhibitingenclosure a thin coating consisting solely of nickel prior to theapplication of heat to obtain the brazing operation, brazing the contactto the member in a heating zone having a temperature lower than themelting temperature of said coating, the heating zone having a maximumtemperature of 2100 F. and an artificial atmosphere wherein the volumeratio of hydrogen and carbon monoxide is substantially near itsequilibrium value for the temperature of the heat application and thecarbon content of the steel member, and controlling the rate of coolingof the member in said artificial atmosphere after the brazing operationfor effecting a substantial increase in the Rockwell hardness of thesteel member and retaining sufficient ductility so that portions of thesteel member will bend at 90 without fracture.

7. The method of producing a breaker arm contact assembly whichcomprises of forming the arm of sheet steel having a carbon contentranging from 0.70% to 0.80%, electroplating directly upon said arm athin coating of pure nickel forming a sealing enclosure, bonding acontact member to the nickel coating in a heating zon having atemperature below the melting point of said nickel coating by fusing acuprous alloy at a temperature that does not exceed 2100 F. in anartificial atmosphere which prevents decarburization, and controllingthe rate of cooling of the arm with its brazed contact after the brazingoperation in an atmosphere which prevents decarburization to impartsimultaneously added strength to the bond between the contact member andthe arm and produce a hardness for the steel member ranging from 30 to45 Rockwell C' scale in which sufficient ductility is retained so thatportions of the arm will bend to a 90 angle without fracture producing abreaker arm assembly having an average fatigue life of at least fivetimes that of an assembly made of low carbon steel operating under thesame con: ditions. 3

8. The method of increasing the fatigue strength of a high carbon steelmember for a make and break contact assembly having a car bon content ofabout 0.75% when the member is subjected to a copper brazing operationfor bonding a tungsten contact to the member which compriseselectroplating the member with a thin coating consisting solely of purenickel prior tov the application of heat to obtain the copper brazingoperation, the copper brazing operation obtained by fusing a copperalloy between the tungsten contact and the nickel coating at atemperature below the flow point of the nickel coating not exceeding2100 F. in an artificial atmosphere wherein the volum ratio of hydrogenand carbon monoxide is substantially near its equilibrium value at 2100F. for a 0.75% carbon steel member, and controlling the rate of coolingof the member in said artificial atmosphere for imparting a hardnessranging from 30 to Rockwell C for the steel member and retainingsuflicient ductility so that portions of the steel member will bend atsubstantially right angles without fracture.

LEO L. VASOLD.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 848,161 Dierig Mar. 26, 1907 1,339,152 Arnold May 4, 19201,650,397 Liebmann Nov. 29, 1927 1,651,891 Hodges Dec. 6, 1927 1,770,839Carpenter July 15, 1930 1,892,607 Bundy Dec. 27, 1932 2,026,344Hollopeter Dec. 31, 1935 2,032,977 Delachaux Mar. 3, 1936 2,123,384Silliman July 12, 1938 2,199,240 Gwyn Apr. 30, 1940 2,301,915 HarringtonNov. 17, 1942 2,315,740 Schoonmaker Apr. 6, 1943 2,419,231 Schantz Apr.22, 1947

1. AN IGNITION BREAKER ARM STRUCTURE COMPRISING A HIGH CARBON STEEL ARM, AN OVERALL SEALING COVER SOLELY OF NICKEL DIRECTLY ENCLOSING SAID ARM, A TUNGSTEN INTERRUPTER CONTACT BRAZED TO SAID NICKEL SEALING COVER, THE BRAZING OF SAID CONTACT TO SAID NICKEL SEALING COVER SECURED BY A CUPROUS BRAZING ALLOY HAVING A MELTING POINT BELOW THAT OF SAID NICKEL COVER RANGING BETWEEN 1600* F. TO 2100* F. FUSED THEREBETWEEN, THE SAID ARM HAVING LAMELLAR PEARLITE CHARACTERISTIC AND A CARBON CONTENT RANGING FROM 0.65% TO 0.80% WITH A HARDNESS RANGING FROM 30 TO 45 ROCKWELL IN THE "C" SCALE HAVING SUFFICIENT DUCTILITY TO PERMIT BENDING PORTIONS OF THE ARM TO WIDE ANGLES WAITHOUT FRACTURE. 